title: Randomized double-blind study of prophylactic treatment with an antihistamine for seasonal allergic rhinitis.
abstract: BACKGROUND
  The efficacy of prophylactic treatment before the start of pollen dispersal for prevention of aggravation of symptoms is unclear. The aim of the present study was to examine the efficacy of prophylactic treatment with an antihistamine for seasonal allergic rhinitis (SAR) using an environmental challenge chamber (ECC).
  
  
  METHODS
  The study was performed in a randomized double-blind manner with a 3-way crossover design. The subjects were 50 patients with SAR caused by Japanese cedar pollen who were randomized for treatment with levocetirizine hydrochloride 5 mg (Xyzal®) or placebo as follows: administration of placebo for 8 days (treatment A), single administration of levocetirizine on day 8 after placebo for 7 days (treatment B) or administration of levocetirizine for 8 days (treatment C). Efficacy in each treatment arm was evaluated based on cedar pollen exposure for 3 h on day 9 in an ECC, following 1-hour exposure on day 8. The primary endpoint was the total nasal symptom score for 12 h on day 9. Other nasal and ocular symptoms were secondary endpoints.
  
  
  RESULTS
  The evaluation was performed in 45 subjects. The total nasal symptom score on day 9 was significantly lower with treatment B compared with treatment A. Treatment C did not show superior efficacy compared with treatment B.
  
  
  CONCLUSIONS
  Our results suggest that early intervention with levocetirizine soon after onset of symptoms may attenuate these symptoms as effectively as prophylactic treatment before pollen dispersal. These results are important from the perspective of patient convenience and reduction of medical costs.
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors.forename: Syuji
authors.initials: S
authors.lastname: Yonekura
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Okamoto
authors.forename: Heizaburo
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Toshioki
authors.initials: T
authors.lastname: Sakurai
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Iinuma
authors.forename: Daiju
authors.initials: D
authors.lastname: Sakurai
authors.forename: Toyoyuki
authors.initials: T
authors.lastname: Hanazawa
mesh_terms: D017332:Cetirizine / Q000008:administration & dosage*; D004311:Double-Blind Method; D006633:Histamine Antagonists / Q000008:administration & dosage*; D006801:Humans; D006255:Rhinitis, Allergic, Seasonal / Q000188:drug therapy* / Q000517:prevention & control*; D016896:Treatment Outcome
chemical_list: D006633:Histamine Antagonists; C472067:levocetirizine; D017332:Cetirizine